How to add suffixes to words ending in 'fer'

When you add a suffix to a word ending in 'fer' you sometimes need to double the 'r', but how do you know when?

When you add a suffixes and the second syllable of the new word is stressed, then you need to double the 'r'.

For example, adding the suffix -ed to the word 'prefer':

prefer + -ed → preferred

However, if the 'fer' is no longer stressed once you've added the suffix, then leave it as a single 'r'.

For example, adding the suffix -able to the word 'prefer'.

prefer + -able → preferable

Here are some further examples of adding suffixes -ed and -ing to words ending in 'fer'.

Notice how the letter 'r' is doubled in the new word.

It helps to say the words out loud so you can hear the syllable you put a stress on.